Power management systems and methods for peer-to-peer network devices

ABSTRACT

A network device of a peer-to-peer network includes a parameter monitoring module. The parameter monitoring module is configured to monitor a network device parameter of the network device. A client traffic window adjusting module is configured to adjust at least one of N client traffic window parameters based on the network device parameter. The N client traffic window parameters include at least one of: a length of a client traffic window; and a number of client traffic windows within a predetermined period. A physical layer device is configured to receive a discovery response signal from a peer-to-peer device during a period of the client traffic window.

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure claims the benefit of U.S. Provisional Application No.61/219,283, filed on Jun. 22, 2009. The disclosure of the aboveapplication is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to power management systems forpeer-to-peer devices.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

A wireless local area network (WLAN) typically permits wirelesscommunication between multiple network devices. A WLAN can be operatedin a number of different modes including, for example, an“infrastructure mode” or an “ad hoc mode”. In a wireless network thatoperates according to the infrastructure mode (referred to herein as an“infrastructure mode network”), all network devices communicate with acentral base station (e.g., an access point). In a wireless network thatoperates according to the ad hoc mode (referred to herein as apeer-to-peer (P2P) network), network devices communicate directly witheach other rather than through a central base station.

Infrastructure mode networks typically include a discovery server and/ora coordination server for discovery and connection setup between networkdevices (e.g., mobile devices). The discovery and coordination serversobtain information regarding network connected peers andapplication-specific information. The discovery and coordination serversare typically located at an access point. A peer-to-peer (P2P) networkgenerally does not include a discovery server, a coordination server, oran access point. Network devices (or peer devices) of a P2P networkcommunicate directly with each other (referred to as WiFi direct).

Discovery of peer devices within a P2P network may include an activephase or find phase. An active phase may include a first network devicetransmitting probe messages to peer devices (i.e., other networkdevices). The first network device may transmit probe messages to join aP2P network and/or to communicate with another network device. A probemessage includes, for example, a basic service set identifier (BSSID)and data rates of the first network device. Peer devices operating in a“listen” mode (at the time a probe message is sent by the first networkdevice) may respond to the probe message by sending a probe responsesignal. The find phase may include toggling between listen and searchmodes.

Network devices typically operate in a “sleep” mode to conserve power.While operating in a sleep mode a network device may be partiallypowered down or fully powered down. Network devices that perform activeand/or passive scanning may transition between operating in a listenmode and a sleep mode.

SUMMARY

A network device of a peer-to-peer network includes a parametermonitoring module. The parameter monitoring module is configured tomonitor a network device parameter of the network device. A clienttraffic window adjusting module is configured to adjust at least one ofN client traffic window parameters based on the network deviceparameter. The N client traffic window parameters include at least oneof: a length of a client traffic window; and a number of client trafficwindows within a predetermined period. A physical layer device isconfigured to receive a discovery response signal from a peer-to-peerdevice during a period of the client traffic window.

In still other features, the systems and methods described above areimplemented by a computer program executed by one or more processors.The computer program can reside on a tangible computer readable mediumsuch as but not limited to memory, nonvolatile data storage, and/orother suitable tangible storage mediums.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a P2P network signal timing diagram illustrating an exampleopportunistic power save method;

FIG. 2 is a functional block diagram of a P2P network in accordance withan embodiment of the present disclosure;

FIG. 3 is a functional block diagram of another P2P network illustratinga group owner in accordance with an embodiment of the presentdisclosure;

FIG. 4 is a P2P network signal timing diagram illustrating anotheropportunistic power save method including a mini-CT window in accordancewith an embodiment of the present disclosure;

FIG. 5 is a P2P network signal timing diagram illustrating yet anotheropportunistic power save method with multiple CT windows during a baseCT window period and in accordance with an embodiment of the presentdisclosure; and

FIGS. 6A and 6B are a logic flow diagram illustrating a method ofoperating a network device (group owner) in accordance with anembodiment of the present disclosure.

DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the disclosure, its application, or uses. For purposesof clarity, the same reference numbers will be used in the drawings toidentify similar elements. As used herein, the phrase at least one of A,B, and C should be construed to mean a logical (A or B or C), using anon-exclusive logical OR. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present disclosure.

As used herein, the term module may refer to, be part of, or include anApplication Specific Integrated Circuit (ASIC), an electronic circuit, aprocessor (shared, dedicated, or group) and/or memory (shared,dedicated, or group) that execute one or more software or firmwareprograms, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

In the following description, a network device may refer to a P2Pdevice, a mobile device and/or a mesh point, a non-mobile device, aservice request device (SRD), user equipment (UE), and/or a mobile node.A network device can include equipment of an end user, such as aprocessor, a radio interface adaptor, etc. A network device may be, forexample, a cellular phone, a smart phone, a personal data assistant(PDA), a printer, a camera, a computer, a router, etc. The networkdevices described herein may comply with the “Wi-Fi Peer-to-Peer (P2P)Technical Specification” of the Wi-Fi Alliance (WFA) Peer-to-PeerTechnical Task Group, which is incorporated herein by reference in itsentirety.

A network device may refer to and/or include a control module, atransceiver, a protocol stack of a transceiver and/or communicationlayers, such as a physical (PHY) layer, a media access control (MAC)layer, a radio link control (RLC) layer, a packet data convergenceprotocol (PDCP) layer, a RRC layer, etc. Although a particular number ofeach network device is shown, any number of each network device may beincluded in a network. Each of the network devices may be considered asa remote network device relative to another network device or peerdevice.

Also, in the following description a beacon and a beacon signal may beassociated with synchronous communication and include a service setidentifier (SSID) or a basic SSID (BSSID), Internet protocol (IP)address, time synchronization bits, characteristic bits, capabilitybits, information elements etc. of a host device (device transmittingbeacon signal). The characteristic bits may indicate characteristics ofa device, such as data rates, frequencies or channels of operation, etc.The capability bits may indicate capabilities of a device, such asInternet access capability, printing capability, half duplex and/or fullduplex mode capability, and communication protocol and applicationcapabilities. Information Elements can contain P2P specific informationabout the transmitting device. A beacon and a beacon signal may betransmitted by a first network device to announce to other networkdevices presence of the first network device and to relay information tothe other network devices. Beacon and beacon signals may be generatedperiodically, or at irregular or sporadic intervals. The timing of thebeacons and the beacon signals may be based on the duration ofcorresponding listen and sleep periods.

In addition, in the following description a probe request and a proberequest signal may be associated with asynchronous communication andinclude a SSID or BSSID, IP address, characteristic bits, capabilitybits, information request bits, information elements etc. of a hostdevice. The information request bits may identify information requestedby the network device that transmits the probe request signal. Theinformation request bits may, for example, be used to requestcharacteristics and capabilities of peer devices. Information Elementscan contain P2P specific information about the transmitting device.

Furthermore, in the following description, a beacon response signal andprobe response signal may include a BSSID, time synchronization bits,characteristic bits, capability bits, information request bits, data(i.e., user) bits, etc of a peer device that responds to a beacon orprobe request signal. The beacon response signal and the probe responsesignal may be generated by a network device that respectively receives abeacon signal or a probe request signal. The beacons, beacon signals,probe request signals, beacon response signals, and probe responsesignals may satisfy IEEE 802.11 standards.

In the “Wi-Fi Peer-to-Peer (P2P) Technical Specification” of the WFAPeer-to-Peer Technical Task Group an opportunistic power save (PS)method is described in section 3.3.3.1. The method is directed topeer-to-peer (P2P) power management that supports power save mechanismsfor P2P group owners and P2P clients of a P2P network. The method allowsa group owner to be absent (operating in a sleep mode) for definedabsent periods. As the group owner is absent for certain periods, aclient traffic (CT) window is introduced for discoverability purposes.The CT window is shorter than a beacon interval. The group owner is ONduring a period of the CT window and is listening for P2P clients.

The CT window may, for example, be defined as being 10-20% the length ofthe beacon interval. As an example, a beacon interval may be 100milliseconds (ms), whereas the length of the CT window may be 10 ms.This provides power savings for the group owner, as the group owner maybe in a sleep mode approximately 90% of the time. The group owner is ina sleep mode more than in an active mode and/or a listen mode toconserve power.

In FIG. 1, a P2P network signal timing diagram illustrating an exampleopportunistic power save method is shown. A P2P network may, forexample, include a group owner GO, a first client Client₁ and a secondclient Client₂. The group owner (GO) may transmit a beacon signal at atarget beacon transmission time (TBTT) after each beacon interval(TBTT₁, TBTT₂ and TBTT₃ and corresponding beacon signals 10-14 areshown).

The timing diagram illustrates times during which the clients Client₁,Client₂ operate in an active mode (e.g., discovery powered ON mode), apower save (PS) mode, and/or a sleep mode. An active mode may refer to aclient performing in a beacon mode (e.g., a probe request mode) or alisten mode. The clients Client₁, Client₂ generate and transmit beaconsignals while operating in a beacon mode. The clients Client₁, Client₂generate and transmit probe request signals while operating in a proberequest mode.

The timing diagram illustrates periods associated with a first series ofoperating modes on a first time axis 20, a second series of operatingmodes on a second time axis 22 and a third series of operating modes ona third time axis 24. The first series of operating modes is associatedwith the group owner GO. The second series of operating modes isassociated with the first client device Client₁. The third series ofoperating modes is associated with the second client device Client₂.

The group owner GO is in the active mode during CT window periods and isin a sleep mode between CT windows periods. The clients Client₁, Client₂may operate in an active mode, a power save (PS) mode and a sleep mode.During the active mode, the clients Client₁, Client₂ may communicate,for example, with the group owner GO. During the PS mode, the clientsClient₁, Client₂ may be partially powered to receive the beacon signals.During the sleep mode the clients Client₁, Client₂ may be partially orfully depowered (OFF).

In the example illustration shown, the first Client₁ does notcommunicate with the GO during a first beacon interval and doescommunicate with the GO during a second beacon interval. The firstClient₁ operates in the PS mode when not operating in the active mode.The first Client₁ may operate in the sleep mode between TBTTs and whennot operating in the active mode.

The second client Client₂ does not communicate with the GO during thefirst and second beacon intervals and operates in the PS mode. Thesecond client Client₂ may not operate in the sleep mode when a TBTT istransmitted, as shown for the first TBTT₁. The second client Client₂ mayoperate in the sleep mode when a TBTT is transmitted, as shown for thesecond TBTT₂.

The PS modes and/or sleep modes may begin when the clients Client₁,Client₂ transmit a power management (PM) mode signal of 1 to the groupowner GO. PM mode signals indicate whether the clients Client₁, Client₂have data to send to the group owner GO. A PM signal of 0 indicates thatthe clients Client₁, Client₂ do have data to send. The PS modes maybegin when the clients Client₁, Client₂ transmit a PM mode signalindicating that they do not have data to send to the group owner GO. Forexample only, a PM mode signal of 1 indicates that clients Client₁,Client₂ do not have data to send to the GO.

Data may be sent between the group owner GO and the clients Client₁,Client₂ during the CT window periods and/or after the CT window periods.The group owner GO may remain in an active state during non-CT windowperiods (between CT window periods and TBTTs) when the GO iscommunicating with one of the clients Client₁, Client₂.

The group owner GO maintains a CT window length (e.g., 10-20 ms) that isadequate to detect a first P2P client. Packet transmission from thefirst P2P client to the group owner can be delayed due to trafficbetween other network devices. The other network devices may becommunicating in the same area using the same medium as the first P2Pclient. The first P2P client backs off from transmitting when otheractivity is detected to prevent interference. The other activity mayinclude any packet transmission on the same medium and/or frequency bandas the group owner GO.

For example, an access point or other group owner may be communicatingwith another network device, such as a Legacy client in a basic serviceset (BSS) of an adjacent network. The Legacy client may not communicatewith the group owner GO, as shown, or may communicate with the groupowner GO and become part of the P2P network. As another example, asecond P2P client may be communicating with the group owner. The firstP2P client may periodically retry transmitting to the group owner basedon detected traffic in the medium.

As a result, the group owner stays awake (ON) for at least apredetermined CT window period (length of CT window). The group ownerremains awake for the predetermined CT window period regardless ofwhether a P2P client sends a packet to the group owner.

Power savings with the above-described method is directly proportionalto the amount of time that he group owner GO is in a sleep mode. As anexample, if the group owner GO has a beacon interval of 100 ms, powersavings is approximately 90% compared to a system where the group ownerGO remains ON 100% of the time. While this power savings is considerablefurther power savings can be provided using the below described systemsand methods.

In FIG. 2, a P2P network (“P2P network”) is shown. The P2P network 40includes peer network devices 42, 44 that each operates in an activemode, a PS mode, and/or a sleep mode. When operating in the active mode,a group owner may transmit beacon signals and listen for beacon responsesignals. Beacon signals may be periodically transmitted by a group ownerto P2P clients. Beacons may be generated, for example, by a group ownerand/or probe request signals may be generated by a P2P client when thereis data to be transmitted to a peer device. When operating in the PSand/or sleep modes, the network devices are partially powered down orfully powered down.

The network devices 42, 44 include respective discovery control modules46, 48 and power management modules 50, 52. The discovery controlmodules 46, 48 include discovery generator modules 54, 56. The discoverygenerator modules 54, 56 determine durations of time in which the peernetwork devices 42, 44 are to operate in the active, PS and sleep modes.The power management modules 50, 52 include CT window adjusting modules58, 60 that adjust duration of CT windows.

In FIG. 3, a P2P network 100 is shown. The P2P network 100 includes agroup owner 102, mobile devices_(1-S) and non-mobile devices_(1-U). S isthe number of mobile devices and is greater than or equal to 1. U is thenumber of non-mobile devices and is an integer greater than or equalto 1. The group owner 102, the mobile devices_(1-S) and the non-mobiledevices_(1-U) are referred to as network devices.

The network devices may operate in active or passive scanning modes anddiscover and communicate directly and wirelessly with each other. Thenetwork devices may discover and communicate directly and wirelesslywith each other. The group owner 102 or host (mobile or non-mobile)device operates in a discovery mode when transmitting beacon and/orprobe signals to identify other active network devices within apredetermined distance of the host device. Each of the network devicesmay operate in a half-duplex mode and/or a full-duplex mode. The networkdevices may communicate using wireless protocols, such as Wi-Fi networkprotocols, wireless local area network (WLAN) protocols, IEEE 802.11wireless network protocols, etc.

The group owner 102 includes a physical layer (PHY) device 103, a mediaaccess controller (MAC) 104, a power management module 106, and acommunication control module 108. The mobile devices_(1-S) andnon-mobile devices_(1-U) may each include the same or similar elementsas the group owner.

The PHY device 103 interfaces the group owner with the mobiledevices_(1-S) and non-mobile devices_(1-U). For example, the PHY device103 transmits or receives beacon signals (i.e., beacons), probe requestsignals, beacon response signals and/or probe response signals to andfrom the mobile devices_(1-S) and non-mobile devices_(1-U). The PHYdevice 103 includes a packet sensing module 110 and handles datatransfer to and from the mobile devices_(1-S) and non-mobiledevices_(1-U). The packet sensing module 110 detects activity in the P2Pnetwork 100 including transmission of beacon signals, probe requestsignals, beacon response signals, probe response signals, packets and/ordata. The activity may be between the network devices and/or betweennetwork devices of an adjacent network (e.g., a Legacy network includinga Legacy client and an access point). The PHY device 103 may includeradio frequency (RF) and baseband circuitry.

The MAC 104 handles generating and parsing of frames. The MAC 104includes a packet generating module 112 and a clear channel assessment(CCA) counter 114. The packet generating module 112 schedules, generatesand/or transfers packets from the communication control module 108 tothe PHY device 103 for transmission to one of the mobile devices_(1-S);and non-mobile devices_(1-U).

The CCA counter 114 indicates whether there is activity in the P2Pnetwork 100 based on an activity signal generated by the packet sensingmodule 110. The packet generating module 112 may randomly back offtransmitting packets based on CCA values 118 associated with the CCAcounter 114. The packet generating module 112 may periodically retrytransmission of the packets. The CCA counter 114 may increment based ondetected IEEE 802.11 packets in a medium of the network devices. The CCAvalues 118 of the CCA counter 114 may be stored in memory 120 and may beaccessible by the power management module 106 and the communicationcontrol module 108.

The CCA counter 114 may, for example, be set to 0 when no activity isdetected. The CCA counter 114 may be a non-zero value when there isactivity. The activity may include packet transmission from a networkdevice other than the group owner 102. The value of the CCA counter 114may be based on the number of packets received by the packet sensingmodule 110. The activity may include packet transmission from a networkdevice that is not in the P2P network 100. A network device isconsidered part of a P2P network when the network device is discoveredand/or accepted by the group owner 102.

The power management module 106 controls power distribution from a powersupply 130 to the PHY device 103, the MAC 104, and the communicationcontrol module 108. The power management module 106 may also controlwhen the group owner 102 is operating in sleep modes. The powermanagement module 106 may be part of the communication control module108. The sleep modes are based on a timing signal (included inbi-directional signals 132) from the communication control module 108.The timing signal may include start times, durations and/or end timesfor listen and/or sleep modes. The durations are adjusted to adjustdiscovery time and power efficiency. The start times, durations and endtimes may be generated based on CT windows, as described below.

The power management module 106 includes parameter monitoring modules,such as a CCA counter monitoring module 136 and a power supplymonitoring module 138. The CCA counter monitoring module 136 monitorsthe CCA counter values 118. The power supply monitoring module 138monitors state of the power supply 130. The state of the power supply130 may include, for example, a battery charge level.

The power management module 106 also includes a CT window adjustingmodule 140. The CT window adjusting module 140 may determine, set, andadjust length(s) of CT window(s) based on the CCA counter values 118and/or the state of the power supply 130. The CT window adjusting module140 may access, adjust, and store CT window lengths and/or a CT windowtable 142 in the memory 120. The CT window table 142 may be based on arelationship between CT window lengths, CCA counter values, power supplycharge levels (battery charge levels), etc. The CCA counter monitoringmodule 136, the power supply monitoring module 138 and the CT windowadjusting module 140 may be firmware based.

The power management module 106 may depower the group owner 102 duringthe sleep modes. During the sleep modes, certain devices or modules mayremain powered, for example, for reactivation purposes. For example, thepower management module 106 may remain active to determine when torepower other devices and/or modules of the group owner 102 subsequentto a sleep mode. The group owner 102 generates beacons or probe responsesignals when reactivated and operating in the discovery mode.

The communication control module 108 processes data transmitted to andreceived from the network devices. The communication control module 108includes a discovery control module 150. The discovery control module150 may be referred to as a P2P state machine and includes a discoverygenerator module 152, a channel selection module 154, a device selectormodule 156, and a user interface module 158. The discovery controlmodule 150 controls discovery operations including the generating,receiving and processing of discovery signals. The discovery controlmodule 150 also controls the accessing and storing of discoveryinformation, such as the characteristics and capabilities of the groupowner 102 and of discovered peer devices. This information is stored inmemory 120 in respective peer files_(1-P), where P is an integer that isgreater than or equal to 2. P is greater than or equal to S, U and/orS+U.

The peer files_(1-P) include device types 160, device names 162, deviceSSIDs 164, device characteristics 166, device capabilities 168, etc. Thedevice types 160 indicate, for example, whether a device is a router, acomputer, a printer, a hub, a server, etc. The device names 162 are userrecognizable names or names that a user can identify. For example, aSSID is not a user recognizable name, as a SSID may be a device specificnumber or other identifier. A device name, as used herein, refers toterms or labels, such as “printer”, “fax”, “contact name”, etc. that auser of the group owner 102 recognizes and can select upon beingdiscovered.

The discovery control module 150 generates timing signals via thediscovery generator module 152 while operating in the discovery mode.The discovery generator module 152 generates the timing signals based onCT window(s) and clock signals from a clock module 170 and stored in thememory 120. The discovery generator module 152 generates listen modetiming values 172 and sleep mode timing values 174, such as start times,durations and/or end times of listen and sleep modes based on the CTwindow(s). The PHY device 103, the MAC 104, the power management module106, the communication control module 108 and/or the discovery controlmodule 150 may be partially or fully powered down when the group owner102 is in the sleep mode.

The channel selection module 154 selects a channel (i.e., frequency orrange of frequencies) on which to transmit a beacon or probe requestsignal. The device selector module 156 selects one or more of thediscovered network devices. The selection is based on a predeterminedcriterion and/or based on a user request signal (included inbi-directional signals 180) received from a user interface 182. Thepredetermined criterion may include device requirements, such asdistance, location, type, data rate, frequency, channel, etc. Forexample, the device selector module 156 may select the one of the mobiledevices_(1-S) that: is within a certain distance from the group owner102; communicates at a predetermined speed; and communicates on aparticular frequency. As another example, the group owner 102 may be acellular phone that is searching for printers and selects Y printers outof X discovered printers. One of the Y printers may be selected as adefault, based on a predetermined criterion and/or based on a userrequest signal. The user may select one of the Y printers, which isdisplayed to the user via a display 184. The user interface 182 may be,for example, a keypad, a touch screen, etc.

One of the mobile devices_(1-S) and non-mobile devices_(1-U) mayrandomly transmit packets to the group owner 102 to determine whetherthe group owner 102 is operating using a mini-CT window. A mini-CTwindow refers to a CT window that is shorter in length than a base CTwindow. For example, a base CT window may be approximately 10-20 ms inlength and a mini-CT window may be less than 10 ms in length. The mobiledevices_(1-S) and non-mobile devices_(1-U) can determine that the groupowner 102 is using a mini-CT window when a response from the group owner102 is not received during a period of the base CT window.

Although the devices and modules of FIG. 3 are shown as distinct items,one or more may be implemented as a single item and/or implemented on asingle IC. For example, the PHY device 103, the MAC 104, the powermanagement module 106, the communication control module 108, the memory120, and the clock module 170 may be implemented as a single item and/oron a single IC.

In FIG. 4, a P2P network signal timing diagram illustrating anotheropportunistic power save method including a mini-CT window is shown. Forthe embodiment of FIG. 4, operating modes for a group owner GO and a P2Pclient of a P2P network are shown. An adjacent network that is operatingusing the same medium and/or frequency band as the P2P network mayinclude an access point (AP) and a non-P2P client (not a member of theP2P network). Operating modes for the AP and the non-P2P client are alsoshown in FIG. 4. The frequency band may include any range offrequencies. Example frequency bands are the IEEE 802.11 2.4 and 5.0 GHzfrequency bands, such as the 802.11A, 802.11B and 802.11G frequencybands.

The group owner GO may transmit a beacon signal at a target beacontransmission time (TBTT) after each beacon interval. The timing diagramillustrates times during which the group owner GO and the P2P clientoperate in an active mode, a PS mode, and/or a sleep mode. The timingdiagram also illustrates communication between the AP and the non-P2Pclient signals 200.

The group owner GO may use a first CT window (CT Window₁ or mini-CTwindow) when the group owner GO does not detect activity on the medium.Activity is detected based on CCA logic and/or a CCA counter. The groupowner GO may use a second CT window (CT Window₂ or base CT window) whenthe group owner GO does detect activity on the medium. The first CTwindow CT Window₁ is shorter in length than the second CT window CTWindow₂. For example only, the first CT window CT Window₁ may be 100microseconds (ps) and the second CT window CT Window₂ may be 10 ms. Theuse of the shorter CT window allows for an increased sleep mode period,as designated by 202. This further conserves power. The sleep modeperiod 202 is increased, as a portion of the sleep mode period is withinthe first CT window₁.

The length of the second CT window₂ may be adjusted based on theactivity detected on the medium, a CCA value, a battery charge level,etc. The group owner GO may remain active while communicating with theP2P client. The group owner GO receives a PM signal of 1 when the P2Pclient does not have data to send to the group owner GO. The group ownerGO receives a PM signal of 0 when the P2P client has data to send to thegroup owner GO. Data may be received from the P2P client during or afterperiods of the CT windows_(1,2). The group owner GO may return to thesleep mode after receiving a PM mode signal of 1 from the P2P client.

The length of the CT windows_(1,2) may be transmitted to the P2P client.The lengths of the CT windows_(1,2) may be sent as part of a discoverysignal, a beacon signal, a probe response signal, etc. The P2P clienttransmits discovery (beacon) response signals based on the lengths ofthe CT windows_(1,2) and the TBTTs. The lengths of the CT windows_(1,2)and the TBTTs may be determined by the group owner GO and provided fromthe group owner to the P2P client.

The length of the mini-CT window is long enough for the P2P client totransmit a packet to the group owner GO. In addition, as the length ofthe mini-CT window is less than the length of the base CT window, thegroup owner GO may be in the sleep mode for an increased amount of time.This further conserves power. For example, during large idle periods,when there are no packets to be transmitted, the group owner GO is awakefor the mini-CT window period (e.g., 100 ps). This is 1/100^(th) of thetime associated with the base CT window.

A P2P client and/or a group owner may detect transmission of a packet bya Legacy BSS. This may be referred to as a ‘hidden’ transmission in viewof the group owner. The group owner may: adjust length of a CT window, amini-CT window, and/or return to or remain in a sleep mode when hiddenpackets are transmitted. For example, the group owner GO increases thelength of the CT window from the first CT window₁ to the second CTwindow₂ upon detecting the hidden packets. The group owner also returnsto the sleep mode after detecting the hidden packets and a PM signal of1 from the P2P client.

In FIG. 5, a P2P network signal timing diagram illustrating yet anotheropportunistic power save method with multiple (e.g., second and third)mini-CT windows 220, 222 during a base CT window period (e.g., secondbase CT window period 224) is shown. For the embodiment of FIG. 5,operating modes for a group owner GO and a P2P client of a P2P networkare shown. An adjacent network that is operating using the same mediumand/or frequency band as the P2P network may include an AP and a non-P2Pclient. Operating modes for the AP and the non-P2P client are also shownin FIG. 5. The group owner GO may transmit a discovery request (beacon)signal at a target beacon transmission time (TBTT) after each discoveryrequest (beacon) interval.

The group owner GO may increase the number of mini-CT windows over abase CT window period, increase the number of corresponding sleep modes,and/or decrease the length of the corresponding sleep modes. As anexample, a first (single) mini-CT window 226 is shown after a first TBTTand during a predetermined or first base CT window period 228. Thesecond mini-CT window 220 and the third mini-CT window 222 are shownafter a second TBTT and during the second base CT window period 224. Thesecond based CT window period is shown as being the same length as thefirst based CT window period. The group owner GO may be in the sleepmode between and after the second and third mini-CT window periods 220,222. The length of the sleep modes subsequent the second and thirdmini-CT window periods 220, 222 may each be, for example, approximately400 μs in length. The length of the first and second base CT windowperiods 224, 228 may be, for example, 10 ms.

Any number of mini-CT windows and corresponding sleep mode periods maybe used during a single predetermined base CT window period. The sleepmodes may be consecutive to the mini-CT window periods. The number ofmini-CT windows may be adjusted based on activity on a medium, CCAvalues, battery charge levels, etc. As shown, the group owner GO maydetect the P2P client (receive a PM signal of 0) during the thirdmini-CT window and not during the second mini-CT window. Thus, theincreased number of CT windows increases the probability that the P2Pclient is detected by the group owner GO.

In FIGS. 6A and 6B, a method of operating a network device (group owner)including a method of determining a length of a CT window is shown. Themethods may be implemented by any of the network devices shown in FIGS.2 and 3. Although the following tasks are described primarily withrespect to the embodiments of FIGS. 3-5, the tasks may be applied toother embodiments of the present disclosure.

At 300, the discovery control module 150 activates a discovery mode todiscover other mobile and non-mobile devices. At 301, the packet sensingmodule 110 monitors activity on a medium. The packet sensing module 110generates an activity signal based on the activity. The activity signalmay indicate when no activity is detected.

At 302, the CCA counter 114 adjusts the CCA value(s) 118 based on theactivity signal. At 303, the CCA counter monitoring module 136 monitorsthe CCA counter and/or tracks the CCA values 118. At 304, the powersupply monitoring module 138 may monitor power supply charge levels,such as battery charge levels of the power supply 130. The CCAmonitoring module and the power supply monitoring modules may bereferred to as parameter monitoring modules that monitor network deviceparameters, such as the CCA values and the charge levels.

At 305, the CT window adjusting module 140 adjusts CT window parameters,such as mini-CT window or CT window length and/or the number of CTwindows within a predetermined CT window period. The CT windowparameters may be stored as part of the CT window table 142. The CTwindow parameters may be adjusted based on activity and/or type ofactivity. The type of activity may refer to whether the activity isassociated with selectable devices, unselectable devices, whether theactivity is associated with the selected frequency band, etc. The CTwindow parameters are adjusted based on the CCA values 118 and/or thepower supply charge levels. The CCA values 118 may be reset to 0 aftereach discovery request signal and/or TBTT.

The CT window adjusting module 140 may increase length of a CT windowand/or increases the number of CT windows to prevent missing a clientresponse signal. The CT window adjusting module 140 may also decreaselength of a CT window and/or decrease the number of CT windows whenthere is a reduced amount of activity on the medium and/or the powersupply charge levels are less than a predetermined threshold. Thisconserves energy. As an example, the CT window adjusting module 140 mayreduce the CT window length and/or the number of CT windows when a powersupply charge level is less than 10%.

At 306 and during the active mode, the discovery generator module 152generates listen mode, sleep mode, and/or CT window timing values (e.g.,start and end CT window times).

At 307, the channel selection module 154 selects one or more frequenciesand/or channels on which to transmit discovery request signal(s). Thediscovery request signal(s) may be one of beacon signal(s) and proberequest signal(s).

At 308, the PHY device 103 transmits the discovery request signal(s) onone or more of the selected frequencies and/or channels and based on atleast one of the listen mode, sleep mode and/or CT window timing values.Discovery request signals may be transmitted at beacon intervals orprobe request intervals.

The discovery request signal(s) may include a P2P information element(IE). The discovery request signals and/or P2P IE may include: CT windowinformation (start and end times and length); an opportunistic powersave (OPS) bit; a notice of absence (NOA) sub-element; a group ownerintent value; security keys; etc. The OPS bit indicates whether thegroup owner is operating in a power save mode. The NOA sub-elementindicates when the group owner GO is to operate in the sleep mode. Thegroup owner intent value may be used to determine which network deviceshould be the group owner.

At 309, the group owner operates in a listen mode. The listen mode maybe enabled by the discovery control module 150 or the power managementmodule 106. The listen mode may have a fixed or random start time,duration and/or end time and is based on the listen mode timing valuesof 172. During the listen mode, the group owner listens for and receivesprobe request signals and sends probe response signals. During thelisten mode, the group owner may also send beacons periodically. Duringthe listen mode, the group owner may also listen for beacons and/orprobe request signals from other mobile and/or non-mobile devices.

At 311, the discovery control module 150 determines whether discovery(beacon or probe) response signals were received. P2P clients sendbeacon or probe response signals to join a P2P network. The discoverycontrol module 150 proceeds to 314 when beacon or probe response signalswere received, otherwise to 330.

At the end of a CT window period and when the CCA counter is 0, there isno activity on the medium. In other words, no packets were transmittedfrom a P2P client or to and/or from a Legacy client. This may bedetermined by the group owner via the CCA counter and the CT windowadjusting module 140. The group owner may return to the sleep mode afterdetermining that there is no activity and/or after receiving one or morePM signals of 1.

At 314, the discovery control module 150 determines whether no devicesare discovered and/or whether unselectable devices are discovered. At315, the group owner may adjust CT window parameters, such as the lengthof a current CT window and/or subsequent CT windows, and/or the numberof CT windows with a predetermined period. The adjustments may be basedon the activity and/or type of activity detected in steps 311. The typeof activity may refer to whether the activity is associated withselectable, unselectable devices, whether the activity is associatedwith the selected frequency band, etc.

At 316, the discovery control module 150 operates in a sleep mode whenno devices are discovered and/or unselectable devices are discovered.The sleep mode may be initiated by the discovery control module 150 orby the power management module 106.

During the sleep mode the power management module 106 may partially orfully deactivate any of the modules and/or devices of the group owner. Aportion of the discovery control module 150 and/or the power managementmodule 208 may remain in an active state during the sleep mode. Thediscovery control module 150 and/or the power management module 208 maywake up modules and/or devices of the group owner subsequent to thesleep mode.

At 319, the user interface module 158 may indicate to a user thediscovered devices for selection by the user. At 320, the deviceselector module 156 may select one of and/or communicate with thediscovered devices. The selection may be based on a user request signaland/or based on a selection criterion, as described above. At 322, thePHY device 103 may transmit unicast signals to the discovered devices toobtain additional information from selected devices. The additionalinformation may include characteristics and capabilities of thediscovered devices. The group owner may attach to the one or more of thediscovered and/or selected devices.

At 324, the discovery control module 150 may deactivate the discoverymode. The group owner may continue to communicate with the selecteddevice. The group owner may remain awake until reception of a PM signalof 1 from the selected P2P device.

At 330, the discovery control module 220 determines whether beacon orprobe request signal(s) are received. The discovery control moduleproceeds to 331 when beacon or probe request signal(s) are received,otherwise to 338.

At 331, the peer device with the highest group owner intent value isdesignated the group owner. Connections between the group owner and P2Pclients are established. The group owner may provide CT windowinformation before or after step 331. At 332, the user interface module158 may indicate to a user the discovered devices that transmitted thebeacon or probe request signal(s) for selection by the user.

At 333, the device selector module 156 selects and/or communicates withthe discovered devices that transmitted the beacon or probe requestsignal(s). The selection may be based on a user request signal and/orbased on a selection criterion, as described above. At 334, thediscovery control module 150 instructs the PHY device 103 to generate abeacon and/or probe response signals, which are transmitted to thediscovered and/or selected devices. The group owner may attach to theselected devices. The group owner may transmit request signals to obtainadditional information from the discovered devices, such ascharacteristics and capabilities of the discovered devices. At 336, thediscovery control module 150 may deactivate the discovery mode.

At 338, the discovery control module 150 may operate in a sleep mode at316, which may be self initiated or initiated by the power managementmodule 106.

The above-described tasks of the methods of FIG. 6 are meant to beillustrative examples; the tasks may be performed sequentially,synchronously, simultaneously, continuously, during overlapping timeperiods or in a different order depending upon the application. Forexample, when operating in a full-duplex mode, a mobile device maytransmit discovery request signals while listening for discovery requestsignals and/or discovery response signals. Thus, 308 and 309 may beperformed during the same time period.

The broad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims.

1. A network device configured to operate in a peer-to-peer network, thenetwork device comprising: a parameter monitoring module configured tomonitor a network device parameter of the network device; an adjustingmodule configured to adjust at least one of N client traffic windowparameters based on the network device parameter, wherein the N clienttraffic window parameters comprise a number of client traffic windowswithin a predetermined period; and a physical layer device configured toreceive a discovery response signal from a peer-to-peer device during aperiod of one of the client traffic windows, wherein the network deviceis in (i) one of an active mode and a listen mode during periods of theclient traffic windows, and (ii) a sleep mode between consecutive onesof the client traffic windows.
 2. The network device of claim 1,wherein: lengths of the client traffic windows are less than a length ofa beacon interval; the network device is in the sleep mode during thebeacon interval; and the network device is one of partially powered downand fully powered down when the network device is operating in the sleepmode.
 3. The network device of claim 2, wherein the network device doesnot receive discovery response signals from peer-to-peer devices when inthe sleep mode.
 4. The network device of claim 1, wherein the clienttraffic windows within the predetermined period are within a beaconinterval of the network device.
 5. The network device of claim 1,wherein: the parameter monitoring module is configured to monitor acharge level of a power supply of the network device; and the networkdevice parameter is the charge level.
 6. The network device of claim 1,further comprising a power supply monitoring module configured tomonitor a charge level of a power supply of the network device, wherein:the adjusting module is configured to adjust the at least one of the Nclient traffic window parameters based on the charge level; theparameter monitoring module is configured to monitor (i) a clear channelassessment counter, and (ii) a clear channel assessment value stored inmemory; the clear channel assessment counter is configured to incrementthe clear channel assessment value based on activity on a medium; andand the network device parameter is the clear channel assessment value.7. The network device of claim 1, wherein: the N client traffic windowparameters comprise a length of first client traffic window, and alength of a second client traffic window; and the second client trafficwindow is subsequent to the first client traffic window.
 8. The networkdevice of claim 1, wherein the adjusting module is configured to adjustlengths of the client traffic windows and the number of the clienttraffic windows within the predetermined period based on the networkdevice parameter.
 9. The network device of claim 1, wherein: thepredetermined period is a base client traffic window period; and alength of the base client traffic window period is greater than each ofthe lengths of the client traffic windows.
 10. The network device ofclaim 9, wherein the length of the base client traffic window is lessthan a length of a beacon interval of the network device.
 11. Thenetwork device of claim 10, wherein the beacon interval includes two ormore of the client traffic windows.
 12. The network device of claim 1,wherein: the physical layer device is configured to receive a firstpower management signal from a peer-to-peer device; the network deviceis configured to operate in the active mode based on the first powermanagement signal; and the adjusting module is configured to adjust theat least one of the N client traffic window parameters based on thefirst power management signal.
 13. The network device of claim 12,wherein: the physical layer device is configured to receive a secondpower management signal from the peer-to-peer device; and the networkdevice is configured to operate in the sleep mode based on the secondpower management signal.
 14. A system comprising: the network device ofclaim 1; and a peer-to-peer client device, wherein the network device isa group owner of the peer-to-peer network and the network device isconfigured to: transmit a beacon signal and then operates in the listenmode; receive a power management signal from the peer-to-peer client;and operate in the active mode based on the power management signal. 15.The network device of claim 1, wherein the adjusting module isconfigured to: operate based on a first client traffic window; detectpacket transmission on a medium on which the network device communicateswith a peer-to-peer client; and operate using a second client trafficwindow that is different in length than the first client traffic windowbased on the packet transmission.
 16. A network device of a peer-to-peernetwork, the network device comprising: a parameter monitoring moduleconfigured to monitor (i) a clear channel assessment counter, and (ii) aclear channel assessment value of the network device, wherein the clearchannel assessment counter is configured to increment the clear channelassessment value based on activity on a medium; an adjusting moduleconfigured to adjust at least one of N client traffic window parametersbased on the clear channel assessment value, wherein the N clienttraffic window parameters comprise at least one of a length of a firstclient traffic window, and a number of client traffic windows within apredetermined period; and a physical layer device configured to receivea discovery response signal from a peer-to-peer device during a periodof the first client traffic window.
 17. A network device of apeer-to-peer network, the network device comprising: a parametermonitoring module configured to (i) monitor a network device parameterof the network device, and (ii) access a clear channel assessment valuestored in memory; an adjusting module configured to adjust at least oneof N client traffic window parameters based on (i) the network deviceparameter, and (ii) the clear channel assessment value, wherein the Nclient traffic window parameters comprise a length of a first clienttraffic window, and a number of client traffic windows within apredetermined period; a physical layer device configured to receive adiscovery response signal from a peer-to-peer device during a period ofthe first client traffic window; and a media access controllerconfigured to generate clear channel assessment value based on activitydetected on a medium.